A normal video signal successively sends out every vertical synchronization period frame images in which gradual changes in the posture of the displayed objects are recorded and displays moving images wherein the object shall be viewed as moving. Here, a frame is a basic period to display one complete frame image, and for example, is equivalent to a vertical synchronization period. Further, a frame image is image data for displaying a single picture which is recorded the movement of the displayed object for each frame. Moreover, moving image data is an assembly of frame image data for displaying a series of movements of the object.
Even in the image generating devices typical of video game machines, moving character images (virtually generated moving objects or subjects) are displayed by successively sending out frame images in which gradual changes are recorded. In this video game machine, the CPU successively transmits frame images of characters, etc., to the video block. In the video block, frame images transmitted from the CPU are displayed. In other words, a video game machine reads in moving image data which are recorded the character's series of movement images ("walking" and "running") from a large capacity storage medium such as a CD-ROM, and displays moving images based on the above.
If it is a simple motion of repeating the same movement, merely storing the moving image data of such a period and repeating that several times will suffice. To display "walking," the period shall be of the time the character puts forward the left leg, puts forward the right leg, and puts forward the left leg again, and by repeating the period, the image of the character walking continuously may be displayed.
However, it is difficult to make a nonexisting, virtually created character perform complex movements. For example, when displaying a character as an athlete in a track and field event, the character starting the approach run from a walking state, gradually gaining speed, and finally spurting are the kinds of images which are required. Since the above movement changes gradually and will not use the same frame images again, moving image data which repeat the fixed movements may not be repeated several times. Therefore, it was necessary to arrange all of the frame images properly in order to display these movements. But since consuming an extensive amount of capacity of memory just to store one moving images, it is practically impossible to implement several events with one game machine.
If the two completely different movements of "walking" and "running" are switched and displayed, the walking state may suddenly shift to the running state, or the opposite movement may be performed, and the picture will be unnatural and lacking reality.
In addition, it takes much time for the manufacturer to produce original image data. Therefore, every time a new movement mode was added to the conventional video game machines, vast amounts of original data had to be inputted, and became a heavy load for the manufacturers supplying the software.